Induction melting processes and apparatus using a water cooled segmented, copper crucible were developed by the US Bureau of Mines, for example, as described in U.S. Pat. Nos. 3,775,091 and 4,058,668. These patents illustrate use of a CaF.sub.2 skull in the crucible and refractory packing material/spacers between the segments. The CaF.sub.2 skull prevents contact between the molten metal and the crucible segments. Typically, the CaF.sub.2 is melted and solidified on the cooled crucible segments to form an insulating lining or skull between the melt and the crucible segments.
U.S. Pat. No. 4,738,713 illustrates an induction melting process wherein a reactive metal is melted in a water cooled segmented, copper crucible in the absence of a CaF.sub.2 lining or skull. In this patent, a refractory packing material is required between the tubular segments of the crucible to avoid molten metal penetration therebetween and subsequent skull locking.
The Diehm et al. U.S. Pat. No. 4,923,508 discloses a ceramicless induction skull crucible having a plurality of upstanding, water cooled metallic fingers that collectively form an upper metallic sleeve of the melting crucible and a water cooled metallic bottom. The crucible fingers are spaced by gaps small enough to avoid penetration of molten metal between the fingers that could produce skull locking.
There is a need in the art for an induction skull melting apparatus and method that avoids water cooled crucible sleeve segments or fingers as well as use of CaF.sub.2 and other refractory skulls and refractory packing materials between segments that can contaminate the melt and also provide improved service in use in melting metal or alloy charges in a production environment.
An object of the invention is to provide induction skull melting apparatus and method that satisfy this need.